Silica and calcite (calcium carbonate) commonly form together in a wide range of waters, particularly at elevated pH. These conditions accelerate silica polymerisation and shift the balance towards calcite precipitation. When the two scales form together, membrane fouling can develop more rapidly and cause a more severe decline in performance than silica alone.

The electron microscope map here shows a layered structure of calcite and silica which is typical for such a system.

Acid cleaning can readily remove calcite from the membrane which will restore performance but may mask the more persistent silica scale. Although this can produce encouraging initial results, membrane performance may deteriorate again over time because the silica remains in place.

This video demonstrates our approach to cleaning a severely scaled membrane. Because this is a restorative clean that is not expected to be performed frequently, the process is designed to maximise cleaning effectiveness. We begin with C-227 bio and clay cleaner to remove any biofilm coating the scale. C-234 acid cleaner is then applied to dissolve the calcite, followed by C-219 silica cleaner to remove the underlying silica scale.

When we cleaned the membrane seen in the video on site, they were restored to an ‘as-new’ condition. Then combined with a transition to our A-119 silica inhibitor we have stopped further scale from forming and allowed the plant to reliably operate.

Do you have a scale problem Contact us today to discuss how we can help solve this.